/** @license
 * DHTML Snowstorm! JavaScript-based Snow for web pages
 * --------------------------------------------------------
 * Version 1.43.20111201 (Previous rev: 1.42.20111120)
 * Copyright (c) 2007, Scott Schiller. All rights reserved.
 * Code provided under the BSD License:
 * https://schillmania.com/projects/snowstorm/license.txt
 */

/*global window, document, navigator, clearInterval, setInterval */
/*jslint white: false, onevar: true, plusplus: false, undef: true, nomen: true, eqeqeq: true, bitwise: true, regexp: true, newcap: true, immed: true */

var snowStorm = (function(window, document) {

    // --- common properties ---

    this.autoStart = true;          // Whether the snow should start automatically or not.
    this.flakesMax = 60;           // Limit total amount of snow made (falling + sticking)
    this.flakesMaxActive = 60;      // Limit amount of snow falling at once (less = lower CPU use)
    this.animationInterval = 40;    // Theoretical "miliseconds per frame" measurement. 20 = fast + smooth, but high CPU use. 50 = more conservative, but slower
    this.excludeMobile = true;      // Snow is likely to be bad news for mobile phones' CPUs (and batteries.) By default, be nice.
    this.flakeBottom = null;        // Integer for Y axis snow limit, 0 or null for "full-screen" snow effect
    this.followMouse = true;        // Snow movement can respond to the user's mouse
    this.snowColor = '#97a0fe';        // Don't eat (or use?) yellow snow.
    this.snowCharacter = '&bull;';  // &bull; = bullet, &middot; is square on some systems etc.
    this.snowStick = false;          // Whether or not snow should "stick" at the bottom. When off, will never collect.
    this.targetElement = null;      // element which snow will be appended to (null = document.body) - can be an element ID eg. 'myDiv', or a DOM node reference
    this.useMeltEffect = true;      // When recycling fallen snow (or rarely, when falling), have it "melt" and fade out if browser supports it
    this.useTwinkleEffect = false;  // Allow snow to randomly "flicker" in and out of view while falling
    this.usePositionFixed = false;  // true = snow does not shift vertically when scrolling. May increase CPU load, disabled by default - if enabled, used only where supported

    // --- less-used bits ---

    this.freezeOnBlur = true;       // Only snow when the window is in focus (foreground.) Saves CPU.
    this.flakeLeftOffset = 0;       // Left margin/gutter space on edge of container (eg. browser window.) Bump up these values if seeing horizontal scrollbars.
    this.flakeRightOffset = 0;      // Right margin/gutter space on edge of container
    this.flakeWidth = 200;            // Max pixel width reserved for snow element
    this.flakeHeight = 200;           // Max pixel height reserved for snow element
    this.vMaxX = 2.5;                 // Maximum X velocity range for snow
    this.vMaxY = 2.5;                 // Maximum Y velocity range for snow
    this.zIndex = 100000;                // CSS stacking order applied to each snowflake

    // --- End of user section ---

    var s = this, storm = this, i,
        // UA sniffing and backCompat rendering mode checks for fixed position, etc.
        isIE = navigator.userAgent.match(/msie/i),
        isIE6 = navigator.userAgent.match(/msie 6/i),
        isWin98 = navigator.appVersion.match(/windows 98/i),
        isMobile = navigator.userAgent.match(/mobile|opera m(ob|in)/i),
        isBackCompatIE = (isIE && document.compatMode === 'BackCompat'),
        noFixed = (isMobile || isBackCompatIE || isIE6),
        screenX = null, screenX2 = null, screenY = null, scrollY = null, vRndX = null, vRndY = null,
        windOffset = 1,
        windMultiplier = 2,
        flakeTypes = 6,
        fixedForEverything = false,
        opacitySupported = (function(){
            try {
                document.createElement('p').style.opacity = '0.5';
            } catch(e) {
                return false;
            }
            return true;
        }()),
        didInit = false,
        docFrag = document.createDocumentFragment();

    this.timers = [];
    this.flakes = [];
    this.disabled = false;
    this.active = false;
    this.meltFrameCount = 20;
    this.meltFrames = [];

    this.events = (function() {

        var old = (!window.addEventListener && window.attachEvent), slice = Array.prototype.slice,
            evt = {
                add: (old?'attachEvent':'addEventListener'),
                remove: (old?'detachEvent':'removeEventListener')
            };

        function getArgs(oArgs) {
            var args = slice.call(oArgs), len = args.length;
            if (old) {
                args[1] = 'on' + args[1]; // prefix
                if (len > 3) {
                    args.pop(); // no capture
                }
            } else if (len === 3) {
                args.push(false);
            }
            return args;
        }

        function apply(args, sType) {
            var element = args.shift(),
                method = [evt[sType]];
            if (old) {
                element[method](args[0], args[1]);
            } else {
                element[method].apply(element, args);
            }
        }

        function addEvent() {
            apply(getArgs(arguments), 'add');
        }

        function removeEvent() {
            apply(getArgs(arguments), 'remove');
        }

        return {
            add: addEvent,
            remove: removeEvent
        };

    }());

    function rnd(n,min) {
        if (isNaN(min)) {
            min = 0;
        }
        return (Math.random()*n)+min;
    }

    function plusMinus(n) {
        return (parseInt(rnd(2),10)===1?n*-1:n);
    }

    this.randomizeWind = function() {
        var i;
        vRndX = plusMinus(rnd(s.vMaxX,0.2));
        vRndY = rnd(s.vMaxY,0.2);
        if (this.flakes) {
            for (i=0; i<this.flakes.length; i++) {
                if (this.flakes[i].active) {
                    this.flakes[i].setVelocities();
                }
            }
        }
    };

    this.scrollHandler = function() {
        var i;
        // "attach" snowflakes to bottom of window if no absolute bottom value was given
        scrollY = (s.flakeBottom?0:parseInt(window.scrollY||document.documentElement.scrollTop||document.body.scrollTop,10));
        if (isNaN(scrollY)) {
            scrollY = 0; // Netscape 6 scroll fix
        }
        if (!fixedForEverything && !s.flakeBottom && s.flakes) {
            for (i=s.flakes.length; i--;) {
                if (s.flakes[i].active === 0) {
                    s.flakes[i].stick();
                }
            }
        }
    };

    this.resizeHandler = function() {
        if (window.innerWidth || window.innerHeight) {
            screenX = window.innerWidth-16-s.flakeRightOffset;
            screenY = (s.flakeBottom?s.flakeBottom:window.innerHeight);
        } else {
            screenX = (document.documentElement.clientWidth||document.body.clientWidth||document.body.scrollWidth)-(!isIE?8:0)-s.flakeRightOffset;
            screenY = s.flakeBottom?s.flakeBottom:(document.documentElement.clientHeight||document.body.clientHeight||document.body.scrollHeight);
        }
        screenX2 = parseInt(screenX/2,10);
    };

    this.resizeHandlerAlt = function() {
        screenX = s.targetElement.offsetLeft+s.targetElement.offsetWidth-s.flakeRightOffset;
        screenY = s.flakeBottom?s.flakeBottom:s.targetElement.offsetTop+s.targetElement.offsetHeight;
        screenX2 = parseInt(screenX/2,10);
    };

    this.freeze = function() {
        // pause animation
        var i;
        if (!s.disabled) {
            s.disabled = 1;
        } else {
            return false;
        }
        for (i=s.timers.length; i--;) {
            clearInterval(s.timers[i]);
        }
    };

    this.resume = function() {
        if (s.disabled) {
            s.disabled = 0;
        } else {
            return false;
        }
        s.timerInit();
    };

    this.toggleSnow = function() {
        if (!s.flakes.length) {
            // first run
            s.start();
        } else {
            s.active = !s.active;
            if (s.active) {
                s.show();
                s.resume();
            } else {
                s.stop();
                s.freeze();
            }
        }
    };

    this.stop = function() {
        var i;
        this.freeze();
        for (i=this.flakes.length; i--;) {
            this.flakes[i].o.style.display = 'none';
        }
        s.events.remove(window,'scroll',s.scrollHandler);
        s.events.remove(window,'resize',s.resizeHandler);
        if (s.freezeOnBlur) {
            if (isIE) {
                s.events.remove(document,'focusout',s.freeze);
                s.events.remove(document,'focusin',s.resume);
            } else {
                s.events.remove(window,'blur',s.freeze);
                s.events.remove(window,'focus',s.resume);
            }
        }
    };

    this.show = function() {
        var i;
        for (i=this.flakes.length; i--;) {
            this.flakes[i].o.style.display = 'block';
        }
    };

    this.SnowFlake = function(parent,type,x,y) {
        var s = this, storm = parent;
        this.type = type;
        this.x = x||parseInt(rnd(screenX-20),10);
        this.y = (!isNaN(y)?y:-rnd(screenY)-12);
        this.vX = null;
        this.vY = null;
        this.vAmpTypes = [1,1.2,1.4,1.6,1.8]; // "amplification" for vX/vY (based on flake size/type)
        this.vAmp = this.vAmpTypes[this.type];
        this.melting = false;
        this.meltFrameCount = storm.meltFrameCount;
        this.meltFrames = storm.meltFrames;
        this.meltFrame = 0;
        this.twinkleFrame = 0;
        this.active = 1;
        this.fontSize = (10+(this.type/5)*10);
        this.o = document.createElement('p');
        this.o.innerHTML = storm.snowCharacter;
        this.o.style.color = storm.snowColor;
        this.o.style.position = (fixedForEverything?'fixed':'absolute');
        this.o.style.width = storm.flakeWidth+'px';
        this.o.style.height = storm.flakeHeight+'px';
        this.o.style.fontFamily = 'arial,verdana';
        this.o.style.cursor = 'default';
        this.o.style.overflow = 'hidden';
        this.o.style.fontWeight = 'normal';
        this.o.style.zIndex = storm.zIndex;
        docFrag.appendChild(this.o);

        this.refresh = function() {
            if (isNaN(s.x) || isNaN(s.y)) {
                // safety check
                return false;
            }
            s.o.style.left = s.x+'px';
            s.o.style.top = s.y+'px';
        };

        this.stick = function() {
            if (noFixed || (storm.targetElement !== document.documentElement && storm.targetElement !== document.body)) {
                s.o.style.top = (screenY+scrollY-storm.flakeHeight)+'px';
            } else if (storm.flakeBottom) {
                s.o.style.top = storm.flakeBottom+'px';
            } else {
                s.o.style.display = 'none';
                s.o.style.top = 'auto';
                s.o.style.bottom = '0px';
                s.o.style.position = 'fixed';
                s.o.style.display = 'block';
            }
        };

        this.vCheck = function() {
            if (s.vX>=0 && s.vX<0.2) {
                s.vX = 0.2;
            } else if (s.vX<0 && s.vX>-0.2) {
                s.vX = -0.2;
            }
            if (s.vY>=0 && s.vY<0.2) {
                s.vY = 0.2;
            }
        };

        this.move = function() {
            var vX = s.vX*windOffset, yDiff;
            s.x += vX;
            s.y += (s.vY*s.vAmp);
            if (s.x >= screenX || screenX-s.x < storm.flakeWidth) { // X-axis scroll check
                s.x = 0;
            } else if (vX < 0 && s.x-storm.flakeLeftOffset < -storm.flakeWidth) {
                s.x = screenX-storm.flakeWidth-1; // flakeWidth;
            }
            s.refresh();
            yDiff = screenY+scrollY-s.y;
            if (yDiff<storm.flakeHeight) {
                s.active = 0;
                if (storm.snowStick) {
                    s.stick();
                } else {
                    s.recycle();
                }
            } else {
                if (storm.useMeltEffect && s.active && s.type < 3 && !s.melting && Math.random()>0.998) {
                    // ~1/1000 chance of melting mid-air, with each frame
                    s.melting = true;
                    s.melt();
                    // only incrementally melt one frame
                    // s.melting = false;
                }
                if (storm.useTwinkleEffect) {
                    if (!s.twinkleFrame) {
                        if (Math.random()>0.9) {
                            s.twinkleFrame = parseInt(Math.random()*20,10);
                        }
                    } else {
                        s.twinkleFrame--;
                        s.o.style.visibility = (s.twinkleFrame && s.twinkleFrame%2===0?'hidden':'visible');
                    }
                }
            }
        };

        this.animate = function() {
            // main animation loop
            // move, check status, die etc.
            s.move();
        };

        this.setVelocities = function() {
            s.vX = vRndX+rnd(storm.vMaxX*0.12,0.1);
            s.vY = vRndY+rnd(storm.vMaxY*0.12,0.1);
        };

        this.setOpacity = function(o,opacity) {
            if (!opacitySupported) {
                return false;
            }
            o.style.opacity = opacity;
        };

        this.melt = function() {
            if (!storm.useMeltEffect || !s.melting) {
                s.recycle();
            } else {
                if (s.meltFrame < s.meltFrameCount) {
                    s.setOpacity(s.o,s.meltFrames[s.meltFrame]);
                    s.o.style.fontSize = s.fontSize-(s.fontSize*(s.meltFrame/s.meltFrameCount))+'px';
                    s.o.style.lineHeight = storm.flakeHeight+2+(storm.flakeHeight*0.75*(s.meltFrame/s.meltFrameCount))+'px';
                    s.meltFrame++;
                } else {
                    s.recycle();
                }
            }
        };

        this.recycle = function() {
            s.o.style.display = 'none';
            s.o.style.position = (fixedForEverything?'fixed':'absolute');
            s.o.style.bottom = 'auto';
            s.setVelocities();
            s.vCheck();
            s.meltFrame = 0;
            s.melting = false;
            s.setOpacity(s.o,1);
            s.o.style.padding = '0px';
            s.o.style.margin = '0px';
            s.o.style.fontSize = s.fontSize+'px';
            s.o.style.lineHeight = (storm.flakeHeight+2)+'px';
            s.o.style.textAlign = 'center';
            s.o.style.verticalAlign = 'baseline';
            s.x = parseInt(rnd(screenX-storm.flakeWidth-20),10);
            s.y = parseInt(rnd(screenY)*-1,10)-storm.flakeHeight;
            s.refresh();
            s.o.style.display = 'block';
            s.active = 1;
        };

        this.recycle(); // set up x/y coords etc.
        this.refresh();

    };

    this.snow = function() {
        var active = 0, used = 0, waiting = 0, flake = null, i;
        for (i=s.flakes.length; i--;) {
            if (s.flakes[i].active === 1) {
                s.flakes[i].move();
                active++;
            } else if (s.flakes[i].active === 0) {
                used++;
            } else {
                waiting++;
            }
            if (s.flakes[i].melting) {
                s.flakes[i].melt();
            }
        }
        if (active<s.flakesMaxActive) {
            flake = s.flakes[parseInt(rnd(s.flakes.length),10)];
            if (flake.active === 0) {
                flake.melting = true;
            }
        }
    };

    this.mouseMove = function(e) {
        if (!s.followMouse) {
            return true;
        }
        var x = parseInt(e.clientX,10);
        if (x<screenX2) {
            windOffset = -windMultiplier+(x/screenX2*windMultiplier);
        } else {
            x -= screenX2;
            windOffset = (x/screenX2)*windMultiplier;
        }
    };

    this.createSnow = function(limit,allowInactive) {
        var i;
        for (i=0; i<limit; i++) {
            s.flakes[s.flakes.length] = new s.SnowFlake(s,parseInt(rnd(flakeTypes),10));
            if (allowInactive || i>s.flakesMaxActive) {
                s.flakes[s.flakes.length-1].active = -1;
            }
        }
        storm.targetElement.appendChild(docFrag);
    };

    this.timerInit = function() {
        s.timers = (!isWin98?[setInterval(s.snow,s.animationInterval)]:[setInterval(s.snow,s.animationInterval*3),setInterval(s.snow,s.animationInterval)]);
    };

    this.init = function() {
        var i;
        for (i=0; i<s.meltFrameCount; i++) {
            s.meltFrames.push(1-(i/s.meltFrameCount));
        }
        s.randomizeWind();
        s.createSnow(s.flakesMax); // create initial batch
        s.events.add(window,'resize',s.resizeHandler);
        s.events.add(window,'scroll',s.scrollHandler);
        if (s.freezeOnBlur) {
            if (isIE) {
                s.events.add(document,'focusout',s.freeze);
                s.events.add(document,'focusin',s.resume);
            } else {
                s.events.add(window,'blur',s.freeze);
                s.events.add(window,'focus',s.resume);
            }
        }
        s.resizeHandler();
        s.scrollHandler();
        if (s.followMouse) {
            s.events.add(isIE?document:window,'mousemove',s.mouseMove);
        }
        s.animationInterval = Math.max(20,s.animationInterval);
        s.timerInit();
    };

    this.start = function(bFromOnLoad) {
        if (!didInit) {
            didInit = true;
        } else if (bFromOnLoad) {
            // already loaded and running
            return true;
        }
        if (typeof s.targetElement === 'string') {
            var targetID = s.targetElement;
            s.targetElement = document.getElementById(targetID);
            if (!s.targetElement) {
                throw new Error('Snowstorm: Unable to get targetElement "'+targetID+'"');
            }
        }
        if (!s.targetElement) {
            s.targetElement = (!isIE?(document.documentElement?document.documentElement:document.body):document.body);
        }
        if (s.targetElement !== document.documentElement && s.targetElement !== document.body) {
            s.resizeHandler = s.resizeHandlerAlt; // re-map handler to get element instead of screen dimensions
        }
        s.resizeHandler(); // get bounding box elements
        s.usePositionFixed = (s.usePositionFixed && !noFixed); // whether or not position:fixed is supported
        fixedForEverything = s.usePositionFixed;
        if (screenX && screenY && !s.disabled) {
            s.init();
            s.active = true;
        }
    };

    function doDelayedStart() {
        window.setTimeout(function() {
            s.start(true);
        }, 20);
        // event cleanup
        s.events.remove(isIE?document:window,'mousemove',doDelayedStart);
    }

    function doStart() {
        if (!s.excludeMobile || !isMobile) {
            if (s.freezeOnBlur) {
                s.events.add(isIE?document:window,'mousemove',doDelayedStart);
            } else {
                doDelayedStart();
            }
        }
        // event cleanup
        s.events.remove(window, 'load', doStart);
    }

    // hooks for starting the snow
    if (s.autoStart) {
        s.events.add(window, 'load', doStart, false);
    }

    return this;

}(window, document));